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Re: Input/Output Power





---------- Forwarded message ----------
Date: Mon, 6 Oct 1997 08:43:02 -0500
From: Gary Johnson <gjohnson-at-kansas-dot-net>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Input/Output Power 

At 08:30 PM 10/3/97 -0600, you wrote:
>
>
>---------- Forwarded message ----------
>Date: Fri, 3 Oct 1997 20:43:51 -0400 (EDT)
>From: Rscopper-at-aol-dot-com
>To: tesla-at-pupman-dot-com
>Subject: Input/Output Power
>
>To the measurement experts:
>
>I put a current shunt in-line at the line to see if I could measure input
>power.  First I measured 250VAC on my fluke for input voltage.  The current
>shunt is 50mv=20A.  I used the fluke on the mV range and fired up the coil.
> The shunt is inside the garage and the coil is in the driveway about 15feet
>away.
>
>The fluke measured 165mv!  This equates to over 60 amps at 250VAC.  I only
>have 30 amp breakers on this line.  Is the reading wrong, or is the breaker
>too slow, or not good for this application????
>
I tend not to take Fluke readings at face value in this environment.  These
are excellent instruments, but will give bad readings when used outside
their design range.  I once taught a service lab for mechanical engineering
juniors where we put a unipolar square wave into two analog meters, one dc
and the other ac, and a Fluke.  The dc meter gave the average value
correctly, the ac meter gave the rms correctly, and the Fluke gave nonsense.
(Actually it gave the rms of the ac portion of the square wave, after the dc
component had been filtered away.)

I suspect that in this environment that the Fluke is picking up rf from the
operating Tesla coil.  To see if the Fluke leads are acting as an antenna,
try measuring the voltage with both leads connected to the *same* end of the
shunt. Theoretically, you will get zero.  I bet the Fluke will read
something greater than zero, and the amount can be changed by rearranging
the leads to change the area of the loop antenna.

Gary Johnson